UNIVERSITY  OF  CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL    EXPERIMENT    STATION 

BERKELEY.  CALIFORNIA 

CIRCULAR  307 

May,  1926 

AMERICAN  FOULBROOD  AND  ITS  CONTROL 

G.  II.  VANSELL 


American  foulbrood  is  the  most  serious  disease  known  to 
apiculturists  today  and  is  responsible  for  large  losses  to  the  beekeeping 
industry.  It  is  extremely  infectious  and  much  more  destructive  than 
European  foulbrood,  although  its  spread  is  usually  not  so  rapid. 
Owing  to  the  extreme  longevity  and  resistance  of  the  causative 
organism  during  the  spore  stage,  the  disease  may  be  harbored  in 
unsuspected  ways  and  appear  suddenly  when  least  expected.  This 
disease  of  the  brood  of  bees  is  very  often  referred  to  simply  as 
foulbrood.  The  name  '^ American"  has  been  applied  to  it  to  distin- 
guish it  from  the  other  type  of  foulbrood,  which  is  now  spoken  of 
as  European  foulbrood.  Neither  of  these  two  diseases  originated  in 
this  country,  but  both  were  prevalent  among  bees  long  before  they 
were  introduced  to  this  hemisphere  from  the  Old  World.  The  name 
''American"  is  therefore  inappropriate  but  is  well  established. 

In  all  probability,  the  disease  is  of  great  antiquity.  It  was 
certainly  known  to  Aristotle  2000  years  ago,  for  he  speaks  of  a 
disease  of  bees  accompanied  by  a  disgusting  odor.  Schirach  in  1769 
referred  to  this  disease  as  did  Dzierzon  in  1882,  but  the  definite 
cause  was  not  known  until  White  discovered  the  organism  {Bacillus 
larvae)  in  1904. 

Seriousness  of  the  Disease. 

Economical  production  of  honey  is  not  possible  in  an  apiary 
where  disease  is  rampant.  The  loss  caused  by  the  destruction  of  bees, 
combs,  honey  and  hives  in  the  earlier  treatment  of  American  foulbrood 
was  so  great  that  many  beekeepers  ceased  operations  because  the 
decreased  production  was  not  met  by  a  commensurate  increase  in  the 
market  price  of  honey. 


15  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 

Symptoms. 

When  American  f oulbrood  is  present,  its  diagnosis  is  usually  very 
definite  because  of  the  distinct  character  of  the  symptoms  which  is 
due  to  the  fact  that  the  bacteria  causing  this  disease  are  generally 
the  only  organisms  present  and  that  they  are  putrefactive  as  well 
as  pathogenic. 

This  disease  most  frequently  kills  the  bee  larvae  in  a  late  stage 
of  development ;  in  fact,  in  a  fair  percentage  of  the  infections,  death 
occurs  after  pupation  has  been  almost  completed.  During  the  latter 
part  of  the  larval  period,  the  brood  cell  is  sealed  over  or  capped. 
The  first  indication  of  infection  is  a  slight  brownish  discoloration  of 
the  normally  white  larva  and  the  loss  of  the  well  rounded  appearance. 


Fig.  1.    Larvae  dead  from  American  foulbrood.     The  dead  body  settles  down  as  it 
dries  to  form  the  adhering  scale.     (From  U.  S.  D.  A.  Bulletin  809.) 

The  larva  gradually  sinks  down  in  the  cell,  and  becomes  darker  in 
color,  until  the  posterior  end  rests  against  the  bottom  of  the  cell. 
(See  fig.  1.)  After  the  larva  has  partially  dried  and  become  dark 
brown  (coffee  colored),  the  most  typical  characteristic  of  the  disease 
manifests  itself.  If  a  grass  blade  or  other  slender  object  is  inserted 
into  the  mass  and  removed,  the  remains  of  the  larva  adhere  to  it  and 
a  thread  of  gummy  substance  may  be  drawn  out  to  a  varying 
distance.  This  ''ropiness"  is  considered  the  final  test  by  the  beekeeper 
in  the  field.  The  larval  remains  continue  to  dr}^  down  until  but  a 
tightly  adhering  scale  remains  in  the  bottom  of  the  cell.  A  character- 
istic odor  is  very  noticeable  with  American  foulbrood.  It  is  usually 
spoken  of  as  a  ^'glue  pot"  odor,  and  once  it  becomes  familiar  to  an 
observer,  its  presence  is  sufficient  for  recognition  of  this  disease. 
Unfortunately  the  odor  does  not  become  pronounced  until  late  in  the 
development  of  the  disease. 

During  the  early  stages  of  American  foulbrood,  the  cappings  over 
the  infected  larvae  are  indistinguishable  from  those  that  cover  healthy 
larvae,  but  later  they  are  often  sunken  and  punctured.     (See  figs. 


CiRC.  370] 


AMERICAN  FOULBROOD  AND  ITS  CONTROL 


2,  3,  4.)  Though  this  symptom  is  not  peculiar  to  American  foulbrood, 
it  is  an  immediate  indication  that  all  is  not  well  in  the  hive.  Many 
of  the  cappings  are  later  entirely  removed  by  the  bees  and  then  the 
dried  scales  can  be  seen. 


W^W'f 


K^^^M0^M 


Fig.  2.  How  American  foulbrood  starts  in  the  bee  colony.  The  white  circles 
indicate  five  cells  in  which  the  larvae  are  diseased.  No  other  infected  cells  could 
be  found  in  this  hive  at  that  time,  June  10,  1919.  (From  Bulletin  333,  Univ.  Wis. 
Agr.  Exp.  Sta.) 


Pupae  may  also  be  attacked  by  this  disease  and  die,  in  which  case 
they  dry  down  through  stages  similar  to  those  in  the  larvae.  (See 
fig.  5.)     The  ''tongue"  of  the  pupa  frequently  adheres  to  the  top  of 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

the  cell  and  may  be  observed  after  the  drying  is  complete.     Queen 

and  drone  brood  are  occasionally  attacked  as  well  as  worker  brood. 

It  sometimes  happens  that  both  European  and  American  foulbroods 

are  present  in  the  same  hive.    When  there  is  a  question  of  uncertainty 


Fig.  3.  Advanced  stages  of  American  foulbrood.  This  frame  was  removed 
from  the  hive  shown  in  Fig.  2,  July  20,  1919.  (From  Bulletin  333,  Univ.  Wis. 
Agr.  Exp.  Sta.) 

as  to  the  diagnosis,  it  is  possible  to  obtain  help  in  the  matter.  Samples 
of  diseased  brood  in  the  comb,  with  no  honey,  can  be  sent  through 
the  mail.    A  wooden  box  such  as  a  cigar  box  makes  a  good  container. 


CiRC.  370] 


AMERICAN  FOULBROOD  AND  ITS  CONTROL 


The  United  States  Department  of  Agriculture,  Bureau  of  Entomology, 
Washington,  D.  C,  or  the  Branch  of  the  College  of  Agriculture,  Davis, 
California,  will  examine  material  whenever  it  is  sent  in.  There  is  no 
charge  for  this  service. 


«#;'  \h'-^;  ^/*"^*.f 


Fig.  4.  Showing  the  scattered  position  of  the  sunken  and  punctured  cappings 
in  a  rather  advanced  stage  of  infection.  This  frame  was  removed  from  the  brood 
nest  and  all  the  healthy  brood  allowed  to  emerge  before  photographing. 

Cause. 

The  causative  bacterium  of  American  foulbrood  is  Bacillus  larvae 
White.  (See  fig.  6.)  It  is  a  motile,  spore-forming  organism  and 
like  all  bacteria  multiplies  very  rapidly  and  its  spores  are  of  extreme 


Fig.  5.  Pupae  dead  from  American  foulbrood.  The  slender  dried  tongue 
adhering  to  the  top  of  the  cell  is  commonly  observed  and  is  a  good  character  for 
diagnosis.     (From  U.  S.  D.  A.  Bulletin  809.) 

longevity.  Spores  kept  at  room  temperature  have  germinated  after 
nine  years,  and  infected  combs  have  remained  infective  for  fifteen 
years.  The  spores  remain  viable  after  exposure  to  boiling  water 
for  ten  minutes.  In  honey  this  resistance  is  even  more  marked  and 
it  may  be  necessary  to  boil  the  honey  for  forty  minutes  to  insure 
complete  sterilization. 


b  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 

The  spores  of  this  organism  are  taken  into  the  intestinal  tract  of 
the  larva  with  its  food,  after  which  they  germinate,  grow,  and  give 
rise  to  the  symptoms  of  the  disease  described  above.  The  effect  of 
the  bacteria  is  gradual  and  the  larvae  die  only  after  they  have  become 
well  developed. 


Fig.  6.     Drawings   of  Bacillus   larvae,   the   causative   organism   of   American 
foulbrood,  in  its  various  stages  of  development.     (From  U.  S.  D.  A.  Bulletin  809.) 


Fundamental  Facts  Concerning  American  Foulbrood. 

1.  The  organism  {Bacillus  larvae)  causing  this  disease  forms 
spores. 

2.  These  spores  are  so  highly  resistant  to  drying,  sunlight,  heat, 
and  similar  influences  that  they  remain  viable  for  years. 

3.  Honey  containing  these  spores,  when  fed  to  healthy  larvae, 
gives  rise  to  a  new  infection.  Thus,  the  robbing  of  one  colony  by 
another  is  a  source  of  great  danger. 

4.  It  is  very  rare  that  an  infection  of  American  foulbrood  dis- 
appears spontaneously,  as  is  often  the  case  with  European  foulbrood. 
This  occurrence  is  so  rare  that  it  may  be  regarded  as  certain  that 
once  the  organisms  are  introduced  into  a  colony,  they  will  cause  its 
destruction  and  that  of  others  in  turn  if  careful  attention  is  not  given. 

5.  So  far  as  known  all  races  of  bees  are  equally  susceptible  to 
American  foulbrood. 

6.  The  scales  resulting  from  decomposed  larvae  adhere  tightly  to 
the  cell  wall  and  cannot  be  removed  by  the  bees. 

7.  The  use  of  spore-infected  honey  in  making  queen  candy  offers 
a  fertile  source  for  distributing  this  disease  from  one  apiary  to 
another. 


CiRC.  370]  AMERICAN  FOULBROOD  AND  ITS  CONTROL  7 

8.  There  is  no  known  method  of  treating  a  colony  successfully 
without  removing  the  bees  from  the  infected  material. 

9.  Bacillus  larvae  is  not  injurious  to  human  beings. 

Treatment. 

The  older  method  of  destroying  the  combs  has  now  been  supplanted 
so  that  it  is  possible  to  treat  the  infected  combs  economically.  Dr.  J.  C. 
Hutzelman,  with  others,  announced  success  through  the  use  of  an 
alcohol-formalin  mixture.  This  solution  is  highly  efficient  and  its 
cost  low  enough  to  permit  thousands  of  gallons  being  used  annually 
at  present.  However,  a  much  cheaper  water-soap-formalin  solution, 
which  can  be  mixed  at  home,  has  proved  thoroughly  satisfactory.  The 
cost  of  the  materials  for  this  mixture  averages  about  one-fifth  that  of 
the  alcohol-formalin  mixture.  In  comparative  trials  of  efficiency, 
no  distinct  advantage  was  found  which  would  justify  the  recom- 
mendation of  one  mixture  over  the  other — both  are  good. 

It  has  been  held  by  some  that  a  water-formalin  mixture  lacks  in 
penetration  power  but  the  presence  of  the  soap  spreader  increases 
this  so  that  this  criticism  can  no  longer  be  justified.  Also,  the  soap 
makes  the  mixture  sufficiently  alkaline  to  prevent  precipitation  of 
paraform  from  the  formaldehyde,  a  process  which  would  weaken  the 
killing  power  of  the  mixture.  Material  of  this  type  which  was 
mixed  in  July,  1924,  is  still  (May,  1926)   being  used  satisfactorily. 

Procedure. 

The  bees  are  shaken  from  the  infected  colony  into  a  clean  hive 
with  foundation.  The  usual  precautions  to  prevent  spreading  the 
disease  by  robbing  are  observed.  If  possible,  a  hospital  yard  should 
be  established  at  least  two  miles  away  from  the  apiary,  where  the 
colony  should  be  moved  before  shaking. 

The  shaking  treatment  consists  primarily  in  the  removal  of  all 
infected  material  from  the  colony  and  in  compelling  the  bees  to  take 
a  fresh  start  by  building  new  combs.  All  implements  that  will  be 
needed,  such  as  a  hive  tool,  lighted  smoker,  drone  trap,  and  queen 
cage  should  be  in  readiness  before  the  operation  is  begun.  The  usual 
practice  is  to  move  the  infected  colony  to  one  side,  placing  a  clean 
hive  with  frames  of  foundation  comb  in  its  place.  The  bees  are  then 
shaken  or  brushed  from  the  foulbrood  combs  in  front  of  the  clean 
hive.  A  spread  newspaper  will  serve  to  catch  the  nectar  which  may 
fall  from  the  combs.  This  paper  should  be  burned  after  the  job  is 
completed  to  destroy  this  source  of  danger.  An  extra  bee-tight  hive- 
body  with  top  and  bottom  should  be  used  to  receive  the  frames,  from 


8  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 

which  the  bees  have  been  dislodged.  After  the  queen  and  most  of  the 
bees  are  in  the  new  hive,  a  queen  and  drone  trap  or  a  strip  of 
perforated  zinc  should  be  placed  over  the  entrance  to  prevent  the 
colony  from  deserting.  Shaking  at  sundown  after  the  field  flight  stops 
will  reduce  the  robbing  danger  greatly. 

If  several  colonies  are  being  treated  at  one  time,  it  may  pay  to 
stack  the  several  hive-bodies  containing  contaminated  combs  over  a 
diseased  colony,  allowing  most  of  the  healthy  brood  to  emerge.  One 
populous  colony  results  from  this  since  all  the  emerging  young  bees 
take  up  the  work  of  the  one  group.  After  two  weeks  this  colony  is 
treated  in  turn  and  all  the  combs  sterilized. 

Some  beekeepers  prefer  to  shake  the  bees  first  on  to  frames 
containing  only  strips  of  foundation  comb  (rather  than  on  full  sheets) 
and  after  four  days  to  shake  the  colony  a  second  time  on  to  full 
sheets  of  foundation  or  drawn  combs. 

If  little  or  no  nectar  is  coming  in  the  bees  must  be  fed  after  48 
hours.  This  stimulative  feeding  will  be  of  great  help  to  the  bees  even 
when  nectar  is  available.  If  clean,  drawn  or  treated  combs  are  on 
hand,  they  may  be  given  to  the  sliaken  colony  after  48  hours.  This 
part  of  the  treatment  is  different  in  no  way  from  the  common  practice 
in  use  when  the  infected  combs  are  burned  or  rendered  for  wax.* 

Hive-bodies  and  hive  parts  from  diseased  colonies  should  be  thor- 
oughly scraped  and  cleaned  before  being  used  again  on  clean 
colonies,  because  the  hive  parts  are  almost  sure  to  become  more  or 
less  smeared  with  infective  honey  during  the  period  of  treatment.  A 
thorough  scrubbing  with  a  cloth  and  running  water  to  remove  all 
traces  of  honey  from  all  hive  parts  will  materially  assist  in  reducing 
the  spread  of  American  foulbrood.  Many  beekeepers,  in  addition  to 
washing,  scorch  out  the  hive  bodies  slightly;  others  dip  them  in  the 
sterilizing  solution.  Both  these  practices  are  good  precautionary 
measures,  as  is  also  the  painting  of  the  cleanly  scraped  bodies  as  well 
as  the  tops  and  the  bottoms. 

Method  of  Comb  Treatment. 

The  process  of  handling  and  treating  the  infected  combs  and 
materials  is  as  follows: 

1.  All  cells  (both  brood  and  honey)  are  uncapped^  and  the  honey 
from  them  is  thrown  out  by  means  of  an  extractor.     (This  honey  of 


*  See  U.  S.  Dept.  Agr.  Farfners '  Bulletin  no.  1084  for  detailed  particulars  on 
the  shaking  treatment  for  American  foulbrood. 

t  If  the  sealed  brood  cells  are  not  opened  in  uncapping,  they  should  be 
punctured  by  scratching  with  a  steel  brush,  curry  comb,  or  similar  tool. 


CiRC.  370] 


AMERICAN  FOITLBROOD  AND  ITS  CONTROL 


course  must  be  handled  with  great  care  and  must  not  be  fed  back  to 
bees  unless  boiled  for  forty  minutes.) 

2.  The  remaining  honey  is  removed  from  the  combs  by  placing  in 
a  vat  and  soaking  twelve  hours  in  water. 

3.  The  ''honey-dissolving"  water  is  thrown  from  the  cells  by 
running  the  combs  through  the  extractor. 

4.  The  empty  wet  combs  are  returned  to  the  dipping  vat.  The 
method  of  filling  the  comb  vat  with  the  sterilizing  solution  is  shown 
in  figure  7,  a  and  h.    By  means  of  a  hoisting  tackle,  the  solution  keg 


'-^ 


Fig.  7.  (a)  An  arraiigcnient  fui'  tilling  the  comb  vat.  Tlie  frames  are  placed 
in  position  for  sterilization  before  the  keg  is  hoisted,  (h)  Showing  use  of  block 
and  tackle  for  hoisting  the  keg  containing  the  sterilizer.  The  solution  flows 
slowly  through  tlie  three-fourths  inch  hose,  thereby  filling  every  cell  in  the  combs. 


is  raised  above  the  level  of  the  top  of  the  vat.  The  keg  is  connected 
with  the  vat  by  a  three-fourths  inch  hose  with  valves  for  regulating 
the  flow,  allowing  the  solution  to  flow  into  and  fill  each  cell  as  the 
level  slowly  rises. 

When  the  vat  is  full  and  all  the  combs  covered,  the  valve  is  closed 
and  the  keg  lowered  to  the  floor.  At  the  end  of  the  immersion  period 
the  valve  is  opened  to  permit  the  solution  to  flow  back  into  the  keg. 
The  vat  should  be  kept  covered  to  prevent  evaporation.  Since  the 
sterilizer   gives  off  formalin   vapor,   which   is   irritating   to   mucous 


10 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION 


membranes,  it  is  best  to  have  the  equipment  in  an  open  screened 
structure  to  allow  the  wind  to  carry  the  vapors  away.  Also  rubber 
gloves  should  be  worn  when  handling  combs  wet  with  the  solution. 

5.  After  forty-eight  hours  the  solution  is  drawn  off,  and  that 
remaining  in  the  cells  is  thrown  from  the  combs  with  an  extractor 
and  saved  for  re-use. 

6.  The  combs  are  thoroughly  dried  and  aired*  for  several  days, 
after  which  they  are  ready  for  use  wherever  they  may  be  needed. 


Fig.  8.  The  dried  adhering  scales  from  larvae  dead  from  American  foulbrood 
are  loosened  by  the  water-soap-formalin.  The  bees  readily  remove  the  loosened 
scales,  and  carry  them  out  of  the  hive. 


The  Solution. 

The  water-soap-formalin  mixture  contains  the  following : 

Water  (soft  preferably)   4  quarts 

Liquid   soap 2  ounces 

Formalin  1  quart 

The  liquid  soap  is  simply  poured  into  the  water.  This  kind  of 
soap  is  recommended  because  it  is  readily  miscible  with  water.     The 

*  The  bees  are  a  little  slow  in  cleaning  out  the  combs  if  the  airing  is  not  given. 
It  takes  much  more  time  for  the  old  scales  to  be  removed  (see  figs.  8  and  9)  and 
the  cells  polished  for  laying  purposes  than  for  honey  storage.  The  bees  will 
prepare  the  combs  during  the  periods  of  little  flow  and  should  be  put  to  this  work 
long  in  advance  of  the  main  flows. 


CiRC.  370]  AMERICAN  FOULBROOD  AND  ITS  CONTROL  11 

formalin  is  then  poured  in  and  the  mixture  stirred.  If  it  is  necessary 
to  use  hard  water,  a  little  more  soap  should  be  used  since  some  of 
it  is  precipitated  by  the  chemicals  in  the  water. 


^ -..-__.- 

••T 

• 

'  • 

••• 

0 

••     . 

% 

• 

V 

• 

* 

Fig.  9.     Healthy  brood  in  all  stages  being  reared  in  American  foulbrood  combs 
that  have  been  treated  with  the  water-soap-formalin  solution. 


Fig,  10.     The  old  method  of  treatment  with  fire.     This  is  still  useful  where  but 
few  colonies  are  infected. 


Summary 

American  foulbrood  is  a  bee  disease  which  is  causing  great  losses 
to  beekeepers.  It  has  been  in  America  almost  since  the  hive  bee  was 
introduced  and  has  been  known  to  beekeepers  since  time  immemorial. 

American  foulbrood  is  caused  by  a  spore-forming  bactrium,  Bacil- 
lus larvae.  In  its  control  it  is  necessary  to  know  the  symptoms 
thoroughly  in  order  to  be  able  to  differentiate  between  this  and 
European  foulbrood,  because  the  two  do  not  require  or  respond  to 
the  same  treatment.  All  combs,  honey,  and  other  material  must  be 
removed  from  the  colony,  giving  the  bees  a  chance  to  reestablish 
themselves  in  the  new  combs. 

It  is  no  longer  necessary  to  destroy  the  infected  combs.  They  can 
be  economically  sterilized  with  a  solution  of  water,  soap,  and  formalin 
by  following  the  methods  outlined  in  this  circular. 


Acknowledgments 

Several  beekeepers  have  tried  this  treatment  in  their  apiaries  and 
all  have  reported  favorably.  The  major  part  of  the  culturing,  in 
connection  with  sterility  tests,  was  done  by  N.  Fiat,  a  graduate 
student,  under  the  direction  of  Dr.  C.  S.  Mudge  of  the  University  of 
California.  Doctors  T.  I.  Storer  and  S.  B.  Freeborn  have  made  many 
helpful  suggestions  in  the  preparation  of  the  manuscript.  This 
opportunity  is  taken  to  express  my  appreciation. 

15m-5,'26 


